Ectropion is the turning out (eversion) of the eyelid. This usually affects the lower eyelids giving the animal a "droopy" eye appearance. Aside from being unattractive, ectropion can result in irritation because it causes exposure of the eyeball and the sensitive inner lining of the lid (conjunctiv...

Entropion is an inward rolling of the eyelids. This can cause the eyelashes or hairs of the eyelids to rub against the cornea (the sensitive, clear outer window of the eye) which is often uncomfortable or painful. This can also lead to serious eye damage by causing corneal ulcers or scar tissue form...

The cornea is the clear outer window of the eye and is made up of three layers: Epithelium - the outermost layer (bathed by tears) Stroma - the middle and largest layer.  This region of the cornea is made up of precisely arranged layers of collagen fibers.  This precise arran...

The retina is the light-sensitive tissue in the back of the eye and is made up of photoreceptor cells called rods and cones. The rods are responsible for vision in low light conditions and the cone cells are responsible for vision in bright light. The retina captures the light that enters the eye an...

The cornea is the clear outer window of the eye and is made up of three layers: Epithelium - the outermost layer (bathed by tears)  Stroma - the middle and largest layer. This region of the cornea is made up of precisely arranged layers of collagen fibers. This undisturbed arrangement is cr...

The vitreous is the clear, gel-like substance that fills the space between the lens and the retina.  This gel aids in keeping the retina positioned against the back wall of the eye. Causes With aging, calcium and other particles can spontaneously settle out within the vitreous. This causes th...

The iris is the colored tissue visible in the eye, and its appearance can vary between species and from animal to animal.  It is rich in blood supply and is made up of tissue called stroma, as well as muscles that control the size of the pupil.  Normally, in bright light, the constrictor (...

  The most common change noted in the eyes of the aging animal is lenticular sclerosis, or hardening of the lens.  This is also sometimes referred to as nuclear sclerosis.  This is a phenomenon well-known to humans - especially as they approach their fourth decade of life and come to...